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    <title>The Struts 2 Request Flow</title>
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<p>In the diagram, an initial request goes to the Servlet container (such as Jetty or Resin) which is passed through a standard filter chain. The chain includes the (optional) <strong>ActionContextCleanUp</strong> filter, which is useful when integrating technologies such as <a shape="rect" href="https://cwiki.apache.org/confluence/pages/viewpage.action?pageId=33343">SiteMesh Plugin</a>. Next, the required <strong>FilterDispatcher</strong> is called, which in turn consults the <a shape="rect" href="actionmapper.html">ActionMapper</a> to determine if the request should invoke an action.</p>

<p>If the ActionMapper determines that an Action should be invoked, the FilterDispatcher delegates control to the <strong>ActionProxy</strong>. The ActionProxy consults the framework <a shape="rect" href="configuration-files.html">Configuration Files</a> manager (initialized from the <a shape="rect" href="strutsxml.html">struts.xml</a> file). Next, the ActionProxy creates an <strong>ActionInvocation</strong>, which is responsible for the command pattern implementation. This includes invoking any <strong>Interceptors</strong> (the <em>before</em> clause) in advance of invoking the <strong>Action</strong> itself.</p>

<p>Once the Action returns, the ActionInvocation is responsible for looking up the proper <strong>result</strong> associated with the <strong>Action result code</strong> mapped in <code>struts.xml</code>. The result is then executed, which often (but not always, as is the case for <a shape="rect" href="action-chaining.html">Action Chaining</a>) involves a template written in <a shape="rect" href="jsp.html">JSP</a> or <a shape="rect" href="using-freemarker-templates.html">FreeMarker</a> to be rendered. While rendering, the templates can use the <a shape="rect" href="struts-tags.html">Struts Tags</a> provided by the framework. Some of those components will work with the ActionMapper to render proper URLs for additional requests.</p>

<div class="confluence-information-macro confluence-information-macro-note"><span class="aui-icon aui-icon-small aui-iconfont-warning confluence-information-macro-icon"></span><div class="confluence-information-macro-body"><p>All objects in this architecture (Actions, <a shape="rect" href="result-types.html">Results</a>, <a shape="rect" href="interceptors.html">Interceptors</a>, and so forth) are created by an <a shape="rect" href="objectfactory.html">ObjectFactory</a>. This ObjectFactory is pluggable. We can provide our own ObjectFactory for any reason that requires knowing when objects in the framework are created. A popular ObjectFactory implementation uses Spring as provided by the <a shape="rect" href="https://cwiki.apache.org/confluence/pages/viewpage.action?pageId=33274">Spring Plugin</a>.</p></div></div>

<p>Interceptors are executed again (in reverse order, calling the <em>after</em> clause). Finally, the response returns through the filters configured in the <code>web.xml</code>. If the ActionContextCleanUp filter is present, the FilterDispatcher will <em>not</em> clean up the ThreadLocal <strong>ActionContext</strong>. If the ActionContextCleanUp filter is not present, the FilterDispatcher will cleanup all ThreadLocals.</p></div>
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